(a) Field of the Invention
This application relates to a system and method for adjusting the pressure in the suspension system of a motorcycle. More particularly, but not by way of limitation, this application relates to a valve system for purging gases that become trapped within the fork tubes or suspension of a motorcycle's fork.
(b) Discussion of Known Art
U.S. Pat. No. 4,807,860 to Simons, which is incorporated herein in its entirety by reference, discloses a system for reducing the gas pressure buildup in the dampeners that are part of the front suspension fork of a motorcycle. More particularly, FIG. 8 of the Simmons patent shows a cap that is mounted at the top end of each of the fork tubes or dampeners, and includes a valve mechanism that opens when the fork tubes are fully extended and allows the escape of gases that have built up within the fork tube.
While the Simons device provides relief for the pressure buildup within the fork's dampeners, the mechanism only provides this relief when the fork's dampeners are fully extended. This type of activation, however, presents significant limitations in that opening the valve passage only when the dampeners are fully extended reduces the amount of excess gas that can be released. The dampeners are more than just dashpots, but include both the dampening mechanism and related spring return mechanism that is used to restore the dampener to the appropriate position or length. Excessive trapped gas stiffens the assembly. Thus, leaving too much gas within the dampeners will not restore the dampeners to their designed resting stage, and thus will not completely solve the problem of excessive gas pressure within the fork's dampeners.
Today's fork dampeners are provided with a cap that is installed on the top of the dampener. Each cap includes a vent hole that is covered with a threaded plug or screw. In order to relieve the pressure from excess air or gas buildup, the user must loosen or remove the threaded plug to allow this air or gas to escape. This means that in a motocross race situation, for example, the user must obtain the appropriate wrench or tool, then undo the plug, and then replace the plug with the use of the wrench or tool. This procedure is time consuming, and if the plug is accidentally dropped, can force the rider lose the race.
One known solution is the Pro-Bleeder, which has been offered for sale by Motion Pro, Inc., of San Carlos, Calif. 94070 for more than one year from the date of this application for patent. The Motion Pro device is a valve that fits into the hole on the fork cap that accepts the plug used for bleeding the trapped air or gas from the fork. The Motion Pro device includes a body with a spring-loaded pushbutton that moves a pushrod through the body to move a plug with an O-ring against an aperture at the end to the body. While the Motion Pro device provides a mechanism that allows rapid release of the trapped air or gas with the push of a button, the design has limitations.
One significant limitation of the Motion Pro design is that it only allows the use of a single O-ring, and relies on a seal that is created by compressing the O-ring against a flat surface at the end of the body. By pressing the O-ring against the flat surface the Motion Pro device relies on the force of the spring to ensure that the O-ring deforms and seals against the flat end of the body. This requires a particularly strong spring, which makes the use of the device more difficult, and places unnecessary stress on the O-ring.
Moreover, the Motion Pro device is particularly well suited for motorcycles that are used on dirt tracks or trails. This environment typically includes large amounts of airborne dust and mud, which can enter the valve mechanism of a device like the Motion Pro device and prevent the proper operation of the O-ring.
Therefore, a review of known devices reveals that there remains a need for a simple device that can be used for rapid, reliable release of excess air or gas trapped in the dampeners or struts of the fork of a motorcycle.
There remains a need for a pushbutton pressure relief valve that can be used in place of the pressure relief plug or screw commonly found on the cap of the dampeners or struts of the fork of a motorcycle, which can effectively keep out contaminants from the sealing mechanism of the pressure relief valve and the internal components of the dampeners or struts of the motorcycle.